Synopsis
Use clozapine blood monitoring correctly, recognise myocarditis and infection warnings promptly, and prevent serious harm from treatment breaks, intestinal hypomotility, interactions and fragmented prescribing responsibility.
- Clozapine prescribing, dispensing and blood results must be coordinated through the monitoring service for the person's registered brand.
- UK Clozaril monitoring is at least weekly for eighteen weeks, fortnightly through week fifty-two and four-weekly thereafter when stable.
- The current UK Clozaril schedule takes precedence over the less detailed harmonised European wording elsewhere in the same SmPC.
- Standard thresholds require immediate stopping if WBC falls below 3.0 × 10⁹/L or ANC below 1.5 × 10⁹/L; service-approved alternative ranges apply only when formally agreed.
- A clozapine concentration checks exposure and toxicity; it does not replace the full blood count or exclude myocarditis.
- Smoking cessation, serious infection and metabolic inhibitors can raise clozapine concentrations and require prompt specialist dose assessment.
- Constipation must be actively sought and treated; bowel monitoring is as essential to everyday safety as collecting blood results.
Key red flags
Fever, sore throat, mouth ulcers or other infection symptoms require an immediate blood count and assessment even when the previous monitoring result was normal.
Severe abdominal pain, distension, vomiting, absent bowel sounds or overflow diarrhoea can indicate life-threatening clozapine-related intestinal hypomotility.
A treatment break exceeding forty-eight hours makes resumption at the previous full dose hazardous because cardiovascular tolerance can be lost.
Investigation priorities
Determine whether current infection symptoms coincide with neutropenia.
Management branches
The patient is receiving maintenance clozapine or moving between clinical settings.
- Verify brand, monitoring-service registration, current blood status and the exact last administered dose.
- Check bowel function, sedation, cardiovascular symptoms, smoking and any new medicine or infection at each relevant contact.
- Ensure supply and the next blood appointment are coordinated, with a named clinician responsible for abnormal results and missed doses.